I. Field
The present disclosure relates generally to communication, and more specifically to automatic gain control (AGC) for a wireless receiver.
II. Background
In a wireless communication system, a transmitter typically processes (e.g., encodes and modulates) data and generates a radio frequency (RF) modulated signal that is more suitable for transmission. The transmitter then transmits the RF modulated signal via a wireless channel to a receiver. The wireless channel distorts the transmitted signal with a channel response and further degrades the signal with noise and interference.
The receiver receives the transmitted signal, conditions the received signal to obtain a baseband signal, and digitizes the baseband signal to obtain samples. The received signal level may vary over a wide range due to various channel propagation phenomena such as fading and shadowing. Hence, the receiver typically performs AGC to maintain the baseband signal level within an acceptable range. The AGC attempts to avoid saturation of receiver circuitry and clipping of an analog-to-digital converter (ADC) used to digitize the baseband signal.
AGC may be performed in various manners. In one conventional AGC scheme, one or more analog variable gain amplifiers (VGAs) are used in the receiver, and the gain(s) of the VGA(s) are adjusted to achieve a fixed baseband signal level. This AGC scheme may utilize analog circuitry to detect the baseband signal level and/or to set the gain(s) of the VGA(s). The analog VGA(s) and detection circuitry may complicate the design of the wireless receiver and add cost.
There is therefore a need in the art for techniques to perform AGC at a wireless receiver in an efficient and cost-effective manner.